Sharing a hack I used to create my own CV axle seal install tool when I replaced mine a few months ago.
I bought a small piece of PVC pipe (2.75" exterior diameter) measured down 5 mm and traced a circle in pencil around the PVC. Wrapped the whole thing in duct tape until I had layers stacked to about 3/8".
Used this to tap in seal with a rubber mallet. Just don't pound on it to the point of deforming the duct tape and you'll stop at that 5 mm depth. Worked great for me and only cost about $2.50 and about 20 minutes of time.